Lithium titanate, which has been developed as a material for an electric storage device, is used as an electrode active material excellent in safety and life property for an electric storage device, in particular, a negative electrode active material for a lithium secondary battery. The use of a lithium secondary battery as a small battery for power supply to a portable device or the like has rapidly spread. Furthermore, a large lithium secondary battery has been developed for use in power generation industries or on vehicles etc. The electrode active material for a large lithium secondary battery requires long term reliability and high input/output characteristics, and the use of lithium titanate as a negative electrode active material, in particular, is promising, due to excellence in safety and life property.
Examples of the lithium titanate include several compounds as described in Patent Literature 1. Patent literature 1 describes compounds represented by a general formula LixTiyO4, where 0.8≦x≦1.4 and 1.6≦y≦2.2, including typical examples LiTi2O4, Li1.33Ti1.66O4, and Li0.8Ti2.2O4. Examples of the known method for producing the lithium titanate include: a wet method (Patent Literature 2) by mixing predetermined amounts of a lithium compound and a titanium compound in solvent, drying the mixture, and firing the dried mixture; a spray drying method (Patent Literature 3) by spray-drying the mixture for drying in the wet method; a dry method (Patent Literatures 1 and 4) by dry-mixing predetermined amounts of a lithium compound and a titanium compound and firing the mixture.